Generally, conventional composite sandwich panels require ribs (L- or U-shaped) to join them with each other and construct a structure. However, such a technique using ribs increases the weight of a constructed structure, makes the construction thereof complex, and makes it impossible to form a planar junction surface because the ribs protrude outwards from the sandwich panel. Furthermore, the coefficient of thermal expansion of ribs which are typically made of aluminum is different from that of the composite sandwich panel. This causes deformation of the structure depending on variation of the environmental temperature.
Moreover, in the case of structures which are used for high-precision aerospace structures such as satellite structures, the deformability thereof with respect to variation of the environmental temperature must be very low, and it must meet requirements such as high strength relative to the weight, high space efficiency of a structure and sufficient durability. However, the conventional composite sandwich panels cannot meet these requirements.